Machine element



De@ 9, YA1952 R. A. WINEFORDNER ETAL 2,621,052

MACHINE ELEMENT Filed Sept. 13, 1949 2 SHEETS-SHEET l Y /TTo/eA/e-YS atentecl Dec. 9, 1952 -MACHINE ELEMENT -Roland A. Winefordner and Leo M. McPheron,

Dayton, Ohio, assignors to General'Motors Corporation, Detroit,iMich., a corporationof Dela- Ware 'ApplicationSeptember 13, 1949, Serial No.f11,5,1369

'5 Claims. l

This invention 'relates .tozan improved arbor for supportigza workfpieceduring -the machining cfa surfacethereof.

It is :among thepbjects of the .present invention to .provde-.an varbor .capable 'of rigidly holding a Lwork.-piece thereon :without appreciably distorting the .natural contour .or shape of .the work-'piecezareaengagingtherarbor.

Anotherv object fof .the1presentinvention.is y to provide a -workepiecezsupporting:arborhaving a plurality rof .pressure l.elementsmll moved toengage' the *work piece beforezlbeing .pressed :against itA with'requal pressurewhereby distortiony of said work fi piece -isiheldl to a iminiinum.v if: not'fentirely eliminated.

Further objects-1.andpadvantagesz of thepresent invention will be apparentfrom the following description, reference being "had tothe :accompanying drawings wherein :a preferred .embodiment ofA the present 1 invent-ion .is clearly shown.

The arbor illustrated .inthe present drawings is particularly designed-to 4receiveand. hold a laminated, ring-shapedassembly such'. as a stator core for a dynamo electric machine. Suchacore comprises a vstack of ring-shaped lamina punched f from sheet metal and held together .by rivets, screws,.or any-Iother.suitablemmeansl :A pluralityof` equally spaced radial-slots vextend from'v the interiorl peripheral edge of leach. lamina, each Vslot Aterminating short of the vouterperipheral edgelthereof. In commercial .production whereV each lamina is--stampedlfroml aisheet of metal the outerv and inner`V peripheral edges "will not befa'bsolu-tely round and inf some instances maybe very slightly ovate. Limited-irregularities such as this are vpermissible inthe inner. annular edge because theyrwould tend only to` vary the lair gap between the inner peripheralY surface of the stator and adjacent annular surface of the rotor revolving within the stator. However, when,` as isfgenerally the case, thevstator is-:assembled in a separatelyj machined 'housing orbetween two-end members of 4van electric machine, then the outer contour of the stator ymust be-substantially true and unvarying so V.as Yto conform with' and-ntf into said 'housing prend. members. Variations allowable inthe inner` peripheralsurface of thestator. if existing insitsouter vsurface Wouldprevent assembly ofthe statorv inthe housing `orend membersrandathus tendto abnormal and expensive scrap. Thus "stator :cores ',are placed on an arbor and their outer vsurface-*machined to Aeliminate .any malformation` and make them conform. to the shape and contour of the member into whichthestator is-to be assembled.

An ordinary arbor in which .pressureelements are positively actuated outwardly vto grip the Work-piece or in .this case the stator ring-assembly placed on the arbor will, incase -the inner peripheral surface is ovate instead of perfectly round, exert distorting lstresses uponthestator ring which distortsits outerwperipheralsurface to be machined. .The pressure. elementengaging the higher .portions .of the teriorsurfacewill begin to exert pressures fattheseareaslbefore other pressure .elements` actually..contactthestator surface. By thetime,theselatterpressure elements engage the workpiece. or .statoron the arbor, the elementswhich rst engagedgitare exerting .an excessive,l distorting pressure .inasmuch as all pressure .elements move concurrently outwardly. The machining. of theputer peripheral `surface of the distorted A-statonwill render it regular and it will remain so .as longas the stator is secured to the `arbor by the pressure elements. However. when `the pressure.. is released and the stator freed to per-n1it1itsremoval from the arbor, it will, to some degree,..if not completelmassume its original shape, Y.the inner contour being again ovate, the outer irregularY and unable to t into the partfor which it was machined.

The arbor of the presentinventionis designed substantially Jto'eliminate distortionaof the work piece inasmuch as the pressure elements :are .all actuated by an elastic body. This-body, when pressure is exerted thereupon, Awill lrnovefall of the pressure elements .into `contact with theadjacent surface ofthe workpiece after whichall are pressed against it withequal force.

In the drawings:

Fig. 1 illustrates an arbor half. insection-.taken along the line I-I .of Fig. 2 and halfdn side elevation, the arbor -being attached Itoa rotating part of a machine such-as a lathe.

Fig. 2 is an end View 0f thearbor, the..upper half in section, thelower half elevation. ,A work piece in theform ofga ring shaped stator core is shown applied to the, arbor. in this view.

Fig. 3 is -an end View of .the main bodyportion of the arbor.

Fig. 4 is a side view of the said main-bodyportion of the arbor. 1vFi. 5 is a sectional View.ofthe partfshownrin Fig. 6 is a flat view of .astator core-forfwhich this arborA was designed.

Referring to the drawings .the varboreonsists vof a main body portionZU which is attachableto the rotating part 2| `of a lathe .or any `other suitable machine to be used for operating on the work piece carried by the arbor. This main body portion of the arbor is detailedly illustrated in the Figs. 3, 4 and 5. It comprises a central tubular portion 22 having an outwardly extending, annular flange at each end. Flange 23, at one end of the central tubular portion 22 is of greater diameter than flange 24 at the opposite end thereof. Screws 25, passing through holes 26 in ange 23 are received by the rotating part 2| of the lathe or machine used to rotate the arbor.

Between the side wall surfaces 21 and 23 of flanges 23 and 24 respectively, the central, tubular portion 22 is radially slotted. In the present design this portion of the arbor has sixteen equally spaced, radial slots 30 the ends of said slots all terminating in the inner and outer peripheral surfaces 3| and 32 respectively.

The flanged end 24 of the main body portion of the arbor is recessed as at 33 and at the bottom of said recess 33 there is an annular groove 34 counterbored therein. The flanged end 23 has a recess of two dinerent diameter portions and 35, the smaller diameter portion 3G having an annular groove 31 provided in its bottom surface.

Recess 33 receives the end ring 40 having a central opening aligning with the central opening in the main body portion 23 of the arbor. An annular flange 4| on the end ring abuts against the end of the arbor and has a series of openings for receiving screws 42 which threadedly engage the arbor to secure the end ring thereon. The portion of end ring which extends into the recess 33 is of two diameters, the larger fitting into said recess, the smaller diameter portion forming an annular space corresponding to and aligning with the annular recess 34 in the arbor body portion 22. This space is occupied by a retractor ring 44 whose outer end extends froi ring 40 into the annular recess 34 of the arbor body. The inner, annular edge of the retractor ring 44, which extends into the recess 34 is tapered, presenting a sloping, camming surface for purposes to be described. Springs in holes 43 provided in ring 4, constantly urge the retractor ring 44 outwardly of ring 48 and into the recess 34 of the arbor body.

At the opposite end of the arbor body a ring 53 similar to ring 40 is provided. A flange 53 on ring has provisions to receive screws by means of which said ring is secured to the arbor body. Ring 5D has a central opening of two different diameters, the smaller one 5| and the larger one 52 both coaxially aligning with the central openr ing in the arbor body portion 22. The larger diameter portion 52 is substantially the same as said arbor body opening. Like ring 40, ring 5l] has a smaller diameter portion at its inner end, forming an annular space 54 which coincides with the annular recess 31 in the arbor body. This space is occupied by a retractor ring 55 which is spring urged outwardly so that its wedge shaped outer end extends into said recess 31. Retractor rings 44 and 55 constantly urged into their respective arbor body recesses 34 and 31 respectively, provide means operative yieldably to maintain the several pressure elements in normal retracted position.

Each slot 3) in the main body portion 22 of the arbor provides a receptacle in which a pressure element or segment 69 is slidably supported. Each pressure element or finger 6B comprises a trunk portion 6| and a cross-head portion 62 so that. as shown in Fig. 2, segment 60 is T-shaped in cross-section. The trunk portion 6| fits slidably in its respective radial slot 30 and its end surface is normally, substantially fiush with the surface 3| in the body portion 22. The crosshead portion is arcuate to correspond to the curvature of the outer surface of arbor body 22 and normally rests upon longitudinal sealing strips 53 secured to said arbor body. Each cross-head portion of a pressure element or segment has a wedge-block G2 secured thereto, which aligns with the adjacent entrance to a stator core slot 53 so as to be able to enter thereinto when the segment 63 is moved radially outwardly of the arbor body 22. The segmented, annular surface presented by the group pressure elements 50 conforms with and is of slightly less diameter than the segmented annular surface 65 presented by the inner edges of the slot teeth 66 of the stator core 61 shown in Fig. 6 and adapted to be placed on the arbor for machining the outer peripheral surface 68 of said stator core.

Every segment or pressure element 6|! has a wedge shaped notch 1U in each end thereof. The notch 13 at one end of a finger 60 has the wedge shaped end of spring loaded retractor ring 44 extending thereinto the engaging sloping surfaces of the notch and the ring therein cooperating yieldably to urge the respective segment inwardly and hold it in normal position. The notch 10 at the opposite end of the segment 60 has the retractor ring 55 extending into it, and the engaging sloping surfaces of said notch and ring 54 also cooperate to urge this end of the segment yieldably into normal position in which the inner end of the segment is substantially flush with the inner annular surface 3| of the arbor body and the cross-head portion is yieldably held upon sealing strips secured to said body.

As mentioned before, end ring 40 has a central opening aligning with and substantially equal in diameter to the central opening in the arbor body 22. On the other hand, end ring 50 at the opposite end of the arbor body has a central opening of two diameters, one substantially equal to and aligning with the opening in the arbor body, the other of smaller diameter but coaxial with said arbor body opening. A piston plug 15 extends ooaxially through the arbor body and its end rings, the main body portion 15 being of the same diameter as the smaller opening in the end ring 5|) so as to be slidable therein. A head or piston portion 11 fitting slidably within the opening in the end ring 4U. The piston plug 15 forms a closed, annular chamber within the arbor said chamber being completely filled with a body of elastic material S such as rubber or any synthetic substitute having the same elastic properties as rubber, for instance being capable of moving or flowing when pressure is exerted thereupon. Figs. 1 and 2 illustrate this body of elastic material and show that the inner ends of the trunk portions of the respective pressure elements 63 are in constant engagement with said body.

The piston plug 15 is hollow, a screw 8| extending therethrough. The head 82 of screw 8| abuts against the outer end of the piston plug head or piston portion 11, the other, threaded end of the screw operatively engaging an interiorly threaded recess in the end of a draw bar 83 which is also threadedly connected to the body portion 13 of the piston plug 15 and has its head 84 engaging the outer surface of the rotatingelement 2|. By this arrangement rotation of the draw bar 83 in the proper direction and prising a rigid core having a coaxial opening; radial passages in the core extending from its outer peripheral surface to the coaxial opening thereon; piston like elements radially siidable in each passage; two oppositely disposed, spring loaded retractors provided in the core, said retractors engaging each piston like element at opposite points, said retractors being operative to resist outward thrust of said elements relatively to the core; an elastic medium in the core opening, constantly engaging all of said elements; a piston in the core opening engaging the elastic medium; and means supported by the core and engaging the piston therein for moving it to compress and displace the medium to urge the piston like elements outwardly of the core against the eect of the retractors.

5. An arbor for supporting a work piece, said arbor comprising a cylindrically shaped core having a coaxial, end to end opening; equally spaced radial slots extending from the core opening to the outer peripheral surface and terminating short of the ends of the core; pressure elements slidable radially in said slots; closure means for one end of the core opening; a spring loaded ring provided at each end of the core, each ring having a camming edge urged into operative engagement with a cooperating cam faced notch in each pressure element, said rings yieldably resisting outward movement of the pressure elements; a body of elastic material in the core opening; a piston in said core opening and actuating means engaging the piston and threaded to the closure means, said actuating means being operative to move the piston for compressing and displacing the elastic body to move the pressure elements against the effect of the spring loaded rings which return said pressure elements to normal position when pressure on the elastic body is released.

ROLAND A. WINEFORDNER.

LEO M. MCPHERON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 574,763 Rudolph Jan. 5, 1897 2,373,907 Olson Apr. 17, 1945 2,410,493 Gideon Nov. 5, 1946 

